1. Field of the Invention
The present invention relates to a decorative mold for forming a concrete surface with an uneven pattern.
2. Description of the Background Art
For the construction work, for example, of river-protection, preparation of residences, improvement of slopes, reform of roads, and retaining walls, the concrete placement technique is employed which is advantageous in all of durability, material cost, execution, and the like. However, the concrete surface formed simply by placing concrete in a concrete placement form is monotonous and is difficult to exhibit a beautiful view in harmony with the region where there are houses, mountains, and the like. Accordingly, in recent years, a demand for the formation of concrete surfaces provided with an artistic design is increased.
As an execution method that can answer such a demand, a methods is suggested wherein a decorative mold made of a foamed material which is formed with an uneven pattern, such as a masonry pattern and a brickwork pattern is attached to a concrete placement form and then concrete is placed in the concrete placement form, so that the uneven pattern of the decorative mold is transferred onto the resulting concrete surface (e.g., Japanese Patent Application Laid-Open No. 107510/1988 and Japanese Utility Model Publication No. 24483/1984).
In the above prior method, as the decorative mold with an uneven pattern on the surface, a molded product of polystyrene type resin foamed particles is used because it is relatively inexpensive, etc.
However, there are problems, that is, for example, since a decorative mold of polystyrene type resin foamed particles is liable to adhere strongly to concrete, it becomes difficult to separate the decorative mold from the surface of the placed concrete, and since a mold of polystyrene type resin foamed particles is relatively low in material strength (i.e., relatively brittle) and poor in flexibility, when the mold is separated from the concrete surface, part of the mold is broken and remains adhered to the concrete surface. Accordingly, that leads to a problem that the execution is laborious because the remnant on the concrete surface after the removal of the mold must be removed by scraping or burning by a burner. Further since the prior decorative mold of polystyrene type resin foamed particles is liable to be broken when it is removed from the concrete surface, the mold cannot withstand to be used repeatedly.
On the other hand, Japanese Utility Model Application Laid-Open No. 129258/1992 describes that when a decorative mold is made of a foamed polypropylene or a foamed poly(ethylene/propylene) copolymer, the releasability of the decorative mold from the concrete surface and the durability of the decorative mold can be improved. However, if a decorative mold comprises simply a molded product of polypropylene type resin foamed particles, there is a problem that, for example, when the decorative mold is bent so that the decorative mold may be removed from the concrete surface, the transfer patterned surface of the mold is cracked and therefore it becomes difficult to use the mold again. Further, the molded product of foamed particles is obtained by filling a mold with foamed particles and heating the mold to cause the particles to be fused together and therefore the thus obtained mold has spaces called voids between the foamed and fused particles. To obtain a strength required for the decorative mold, although it is necessary to use foamed particles relatively low in expansion ratio, the molded product obtained by using foamed particles low in expansion ratio is apt to be formed with a number of large voids in the surface, so that there are such problems that the marks of these voids also are transferred to the concrete surface to degrade the appearance and the concrete comes into the voids to lower the releasability of the mold.
Further, sometimes the uneven patterned surface of the decorative mold is coated with a coating material for the purpose of coloring the concrete surface, and if there are a number of large voids in the uneven patterned surface of the decorative mold, a problem surfaces that the coating material comes into the voids and the coating material is difficult to be transferred onto the concrete surface.